12 research outputs found

    Hydroconversion of Methyl Laurate as a Model Compound to Hydrocarbons on Bifunctional Ni<sub>2</sub>P/SAPO-11: Simultaneous Comparison with the Performance of Ni/SAPO-11

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    The bifunctional Ni<sub>2</sub>P/SAPO-11 was tested for the hydroconversion (involving deoxygenation and hydroisomerization) of methyl laurate as a model compound to hydrocarbons. The influences of reaction conditions, catalyst stability, and catalyst deactivation were investigated. For comparison, the performance of Ni/SAPO-11 was also examined. The result shows that the increase of temperature and the deceases of weight hourly space velocity (WHSV) and H<sub>2</sub> pressure favored the conversion of methyl laurate meanwhile promoted the decarbonylation and hydroisomerization as well as cracking reactions. Apart from the Ni sites that were dominating for deoxygenation, the acid sites also affected the deoxygenation pathway. Due to more medium strength acid sites, Ni/SAPO-11 gave higher selectivity to isoalkanes and more preferentially catalyzed the hydrodeoxygenation pathway to produce the C12 hydrocarbons than Ni<sub>2</sub>P/SAPO-11. During the test for 101 h, Ni<sub>2</sub>P/SAPO-11 exhibited greatly superior stability to Ni/SAPO-11 for the deoxygenation of methyl laurate, while both Ni<sub>2</sub>P/SAPO-11 and Ni/SAPO-11 were deactivated for the hydroisomerization. Under the condition of 360 °C, 3.0 MPa, WHSV of 2 h<sup>–1</sup>, and H<sub>2</sub>/methyl laurate molar ratio of 25, the conversion of methyl laurate was close to 100% and the total selectivity to isoundecane and isododecane decreased from 36.9% to 28.6% on Ni<sub>2</sub>P/SAPO-11. To explore the catalyst deactivation, the fresh and the used catalysts were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, Raman spectroscopy, and N<sub>2</sub> adsorption–desorption. The sintering of Ni particles and carbonaceous deposit contribute to inferior stability of Ni/SAPO-11 for both deoxygenation and hydroisomerization, while no obvious sintering of Ni<sub>2</sub>P particles took place and the carbonaceous deposit mainly led to the loss of the activity for hydroisomerization on Ni<sub>2</sub>P/SAPO-11. We propose that carbonaceous deposit mostly formed on the acid sites that are indispensible for hydroisomerization

    Enantioselective Multicomponent Reaction for Rapid Construction of 1,2,5-Triol Derivatives with Vicinal Chiral Centers

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    1,2,5-Triol derivatives with vicinal chiral centers have been synthesized from simple starting materials by one-pot method in good yields and with an excellent enantioselectivity. This process was promoted by a chiral secondary amine and iridium­(I) cocatalyzed three-component reaction of aryldiazoacetates and alcohols with enals as electrophiles followed by a reduction with NaBH<sub>4</sub>. Iridium­(I)-associated oxonium ylide intermediates were efficiently generated and successfully trapped by the amine-activated enals via a selective 1,4-addition manner, generating enantioselective three-component coupling products

    Enantioselective Multicomponent Reaction for Rapid Construction of 1,2,5-Triol Derivatives with Vicinal Chiral Centers

    No full text
    1,2,5-Triol derivatives with vicinal chiral centers have been synthesized from simple starting materials by one-pot method in good yields and with an excellent enantioselectivity. This process was promoted by a chiral secondary amine and iridium­(I) cocatalyzed three-component reaction of aryldiazoacetates and alcohols with enals as electrophiles followed by a reduction with NaBH<sub>4</sub>. Iridium­(I)-associated oxonium ylide intermediates were efficiently generated and successfully trapped by the amine-activated enals via a selective 1,4-addition manner, generating enantioselective three-component coupling products

    DR2539 binds to the MntH promoter DNA fragment in a Mn(II)- and Fe(II)-dependent manner.

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    <p>(A) Schematic of <i>dr1709</i> promoter (p1709a and p1709b) DNA sequence region. The inverted repeat region is shown by the inverted arrows. (B) DR2539 binding to p1709b with increasing quantities of DR2539 and 25 µM Mn(II). (C) and (D) EMSA analysis was performed using DR2539 and p1709b with increasing concentration of Mn(II) or Fe(II). RBS, ribosome binding site; Start, transcription start codon. p1709a and p1709b sequence regions are underlined by straight lines and dashed lines, respectively.</p

    Sequence alignment of the metal binding sites of DR2539 with other DxtR/MntR family members.

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    <p>ScaR (<i>Streptococcus gordonii</i>), SloR (<i>Streptococcus suis</i>), LCAS (<i>Lactobacillus casei</i>), SirR (<i>Corynebacterium glutamicum</i>), TroR (<i>Treponema pallidum</i>), TroR (<i>Treponema denticola</i>), IdeR (<i>Mycobacterium tuberculosis</i>), DtxR (<i>Corynebacterium diptheriae</i>), DR2539 (<i>Deinococcus radiodurans</i>), MntR (<i>Staphylococcus aureus</i>), MntR (<i>Escherichia coli</i>), and MntR (<i>Bacillus subtilis</i>). The sequences were aligned using the CLUSTAL W software. Residues shaded with black represent metal-binding sites that have been studied while residues shaded with grey represent predicted metal binding sites.</p

    DR0865 binds to the promoter of MntABC in an ion-dependent manner.

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    <p>(A) and (B) DR0865 binding to p2523 and p2284 as the concentration of DR0865 increased. (C) Wild-type R1, <i>dr2539</i> null mutant (<b>Δ</b><i>dr2539</i>), and <i>dr0865</i> null mutant (<b>Δ</b><i>dr0865</i>) were cultured on TGY plates overlaid with filter discs saturated with 1 M solution MnCl<sub>2</sub>. (D) The zone of inhibition was measured from edge of disc after three days. *, <i>P</i><0.05. Data represent the means±deviations of three independent experiments.</p

    His98 plays an important role in DNA binding activity of DR2539.

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    <p>(A) 10 µl cell dilution was dripped on the TGY plate to which 6 mM of Mn(II) had been added. The cells were cultured for 3 days. (B) H98Y mutant and wild-type DR2539 proteins were incubated with p1709b at different concentrations of Mn(II). (C) Quantification of the fluorescence intensity of binding bands was performed using ImageJ. *, <i>P</i><0.05.</p

    Mn(II) and Fe(II) modulate the binding activity of DR2539 <i>in vivo</i>.

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    <p>(A) Effects of divalent metals (50 µM) on expression of pRAZH in <i>D. radiodurans</i>. Data shown are the means ± standard deviations of three independent experiments. (B) Effects of Mn(II) (squares) and Fe(II) (circles) on the expression of pRAZH in wild-type samples expressing DR2539. (C) Effects of Mn(II) (squares) and Fe(II) (circles) on the expression of pRAZH in the <i>dr2539</i> null mutant. (D) Rea-time PCR analysis of the <i>dr1709</i> gene expression using <i>dr0089</i> as internal control gene. Longitudinal axes indicate the change fold of <i>dr1709</i> mRNA relative to controls. Control cells were cultured in medium without Mn(II). *, <i>P</i><0.05 relative to control. The data are the means ± standard deviations of three independent experiments.</p

    H<sub>2</sub>O<sub>2</sub> sensitivity in <i>D. radiodurans</i> treated with dAMP, dTMP, dCMP or dGMP.

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    <p>Sensitivity of <i>D. radiodurans</i> to 50 mM H<sub>2</sub>O<sub>2</sub> with the addition of DNA fragments (3.6 mg/ml), dNMPs, dAMP, dTMP, dCMP or dGMP (10 mM for each). Each data point represents the mean±SD of three replicates. R1, <i>D. radiodurans</i> wild type strain.</p

    Addition of extracellular dGMP increases the activity of KatA in <i>D. radiodurans</i>.

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    <p>(A) Extracellular dGMP (2.5 mM) increased the activity of KatA, but not KatB. (B) Extracellular dGMP (2.5 mM) had no effect on the activity of SOD. (C) and (D) Quantification of the intensity of bands was performed using ImageJ. Each sample contains 80 µg of total protein. Values are the mean ± standard deviation of three independent measurements. R1, <i>D. radiodurans</i> wild type strain; KatA, catalase A; KatB, catalase B.</p
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